• Title/Summary/Keyword: melting time

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Synthesis of Functional Copolyester, its Blend with PET, and Properties of Carbon Black Dry Color (기능성 폴리에스테르 공중합체의 합성, PET와의 블렌드 및 카본 블랙 Dry Color의 물성)

  • Park, Lee Soon;Lee, Dong Chan;Kim, Jin Kon;Huh, Wan Soo
    • Applied Chemistry for Engineering
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    • v.7 no.3
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    • pp.496-503
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    • 1996
  • Aromatic and aliphatic copolyesters for the dispersing agent were synthesized by two stage reaction, esterification and polycondensation. Copolyesters were blended with PET in the melt state and their thermal and rheological properties were investigated. From GPC analysis Mn's and Mw's of copolyesters were about 30000 and 65000g/mol, respectively. From DSC experiment copolyesters had melting range of 90150C90150C. Copolymer composition was in good agreement with comonomer feed ratio from 1H1H-NMR analysis. Copolyesters and SPA (standard sample) were blended with PET in the melt state. From DSC experiment, copolyesters and SPA were miscible with PET. From the dynamic melt viscosity experiment, melt viscosity of blended sample was increased as the content of aromatic copolyester was increased, while it was decreased as the content of aliphatic and SPA were increased. As for volume resistivity of dry color containing carbon black and copolyesters with dispersing time, aromatic copolyester showed highest value. It was conferred from this result that aromatic copolyester was the best dispersing agent for carbon black in PET resin.

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Forged Product Characteristic and Cold Rolling Simulation for High-Nitrogen Stainless Steel (HNS) (TP304계 고질소 스테인레스강의 단조특성과 냉간압연 모사)

  • Lee, M.R.;Lee, J.W.;Kim, B.K.;Kim, Y.D.;Shin, J.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.310-313
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    • 2009
  • Several high nitrogen stainless steel ingots(100kg) were fabricated with changing Ni and [N]2[N]2 contents by Pressurized Vacuum Induction Melting(P_VIM). After free forging process, chemical compositions, microstructure and mechanical properties were estimated. Hardness was increased with the increase of [N]2[N]2 content. Furthermore, microstructure including a lot of tempering twins was observed with optical microscope. Mechanical properties were estimated as function of solution treatment temperature and cooling method(air/water) under duration time of 1 hr on sample that were fabricated with Ni content under the atmospheric [N]2[N]2 pressure. At solution treatment range of 10501100C10501100C, hardness was decreased with the increase of solution temperature and there were little discrepancy of microstructure and hardness with cooling method. Computer simulation was carried out in order to inspect pass schedule in cold rolling process. When the condition of simulation was roll speed of 2.5mpm, rolling rate 15171517 per pass, it was ascertained that the formation such as deformation by sticking and lamellar sliver etc. was restricted from a simulation.

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Effects of Moisture Content on Recrystallization of Rice Starch Gels (쌀전분겔의 재결정화에 미치는 수분함량의 영향)

  • Baik, Moo-Yeol;Kim, Kwang-Joong;Cheon, Ki-Cheol;Ha, Yeon-Chul;Kim, Wang-Soo
    • Korean Journal of Food Science and Technology
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    • v.29 no.5
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    • pp.939-946
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    • 1997
  • Effects of moisture content on the gelatinization and recrystallization of non-waxy and waxy rice starch gels were investigated by differential scanning calorimetry (DSC). The recrystallization rates of the starch gels containing various moisture contents (4070(4070 were analyzed by Avrami equation. The waxy rice starch had higher gelatinization temperature and enthalpy than non-waxy one. The highest degrees of recrystallization in both rice starch gels stored at 4C4C were shown at 40%, and recrystallizations above 80% moisture content were not found. The degree of recrystallization of waxy one was higher than that of non-waxy one in the range of 40 to 60% moisture content. The Avrami exponents (n) of both rice starch gels were near to 1.0 and the time constant (1/k) was increased with increasing moisture content in the range of 40 to 70% moisture content. The recrystallization rate of waxy rice starch gel was slower than that of non-waxy one. The recrystallization of rice starch gels could be explained by the change of ice melting enthalpy during storage. The Wg's, represented the maximum practical amount of plasticizing water, were about 29.9% and 28.2% for non-waxy and waxy rice starch gels, respectively.

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KCCH Medical Cyclotron Operation for Neutron Therapy and Isotope Production (1989) - A Technical Report - (중성자 치료와 동위원소 생산을 위한 KCCH 의학용 싸이클로트론의 운영 (1989))

  • Kim, Byung-Mun;Kim, Young-Sear;Bak, Joo-Shik;Lee, Jong-Du;Yoo, Seong-Yul;Koh, Kyung-Hwan
    • Journal of Radiation Protection and Research
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    • v.15 no.2
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    • pp.113-122
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    • 1990
  • After four years of planning, equipment acquisition, facility construction and beam testing, the KCCH cyclotron facility was put into operation in November1986. Now the KCCH cyclotron(MC-50) has been used for four years in neutron therapy and radioisotope production. Up to December 1989, 179(1852 sessions) patient have undergone neutron therapy. Radioisotope production for nuclear medicine use was started from March 1989 after extensive work to overcome target transport, target melting, beam diagnostic and chemical processing problems. This status report introduces the cyclotron facility, and the experiences of neutron therapy and isotope production with the MC-50 cyclotron. Besides, the operation results and the general troubles of the MC-50 during 1989 are summarized. Total operation time was 1252.5 hours. Four hundred hours were used for neutron therapy of 599 treatment sessions and 832.5 hours for radioisotope production. Total amount of produced raioisotope was 1695 mCi(Ga-67 : 1478mCi, Tl-201 : 107 mCi, I-123 : 25mCi, In-111 : 85mCi). Twenty hours were used for scheduled beam testing. In 1989, 882% of the planned operation were performed on schedule and this rats is improved remarkably compared to 71.0% in 1988.

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Studies of Solid-Liquid Phase Equilibria for Mixtures of N-vinyl-2-pyrrolidone+2-pyrrolidone and Growth Rate of N-vinyl-2-pyrrolidone Crystal Using Melt Crystallization (N-vinyl-2-pyrrolidone과 2-pyrrolidone 혼합물의 고-액 상평형 및 용융결정화를 이용한 N-vinyl-2-pyrrolidone의 결정성장속도 연구)

  • Kim, Sun Hyung;Seo, Myoung Do;Tak, Moon Seon;Kim, Woo Sik;Yang, Dae Ryuk;Kang, Jeong Won
    • Korean Chemical Engineering Research
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    • v.51 no.5
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    • pp.587-590
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    • 2013
  • Solid-liquid equilibria for mixtures composed of n-vinyl-2-pyrrolidone (NVP) and 2-pyrrolidone were measured as a basic study for the melt crystallization process to remove 2-pyrrolidone as impurity included in NVP. A differential scanning calorimeter (DSC) and a crystallizer were used and the experimental results obtained from two methods were similar. The mixture showed a eutectic system which has a single composition at the minimum melting temperature. Calculation results from simple thermodynamic equations were found in general agreements with present data. To determine the growth rate of NVP crystal which is important for the design of crystallization process, thicknesses of the crystal were measured with the time using a layer melt crystallizer. The growth rates increased as cooling temperatures decreased. Heat transfer coefficient correlated from present data was found to successfully describe the crystal growth behavior.

Development of Chitosan Coated Solid Lipid Nano-particles Containing 7-Dehydrocholesterol (7-디하이드로콜레스테롤을 함유한 키토산 코팅 처리 Solid Lipid Nano-particle의 개발에 관한 연구)

  • Lee Geun-Soo;Kim Tae-Hoon;Lee Chun-Il;Pyo Hyeong-Bae;Choe Tae-Boo
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.31 no.2 s.51
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    • pp.141-146
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    • 2005
  • Unstable cosmetic active ingredients could rapidly break down in chemical and photochemical process. Therefore, it has become a very important issue to encapsulate active ingredient for the stabilization. 7-Dehydrocholesterol (7-DHC), a precursor of vitamin D3D3, has been shown to increase levels of protein and mRNA for heat shock protein in normal human epidermal keratinocytes. However, topical dermal application of 7-DHC is restricted due to its poor solubility and chemical unstability. In this study, 7-DHC was incorporated into nano-emulsion (NE), solid lipid nano-particle (SLN), and chitosan coated solid lipid nano-particle (CASLN), respectively. In order to prepare NE and SLN dispersion, high-pressure homogenization at temperature above the melting point of lipid was used Hydrogenated lecithin and polysorbate 60 were used as stabilizer for NE and SLN. CASLN was prepared by high speed homogenizing after adding chitosan solution to the SLN dispersion and showed positively charged particle properties. Decomposition rate of 7-DHC in NE, SLN and CASLN was studied as a function of time at different temperature. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies were performed to characterize state of lipid modification. It appeared that CASLN is the most effective to stabilize 7-DHC and may be used for a useful topical dermal delivery system.

Magenetic Properties of Nd-Fe-B-Co-based Melt-spun Ribbons an dTheir Bonded Magents (Nd-Fe-B-Co계 급냉리본과 Bond 자석의 자기적 성질)

  • Gang, Gye-Myeong;Gang, Gi-Won;O, Yeong-Min;Song, Jin-Tae
    • Korean Journal of Materials Research
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    • v.3 no.2
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    • pp.175-184
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    • 1993
  • Abstract Co-and/or AI-added Nd-Fe-B-based magnetic alloys were fabricated by using vacuum induction melting frunace, and melt-spun ribbons were made of the magnetic alloys with single roll rapid quenching method. The variation of magnetic properties of the melt-spun ribbons as a function of Cuwheel velocity (Vs) were investigated. Bonded magnets were made of the optimally quenched ribbon fragments, and the magnetic properties of the melt-spun ribbons and the bonded magnets were studied, relating to the microstructure and crystalline structure. Cu-wheel surface velocity had a strong effect on the magnetic properties of the melt-spun ribbons, and the maximum properties were obtained around Vs =20m/sec. The optimally quenched ribbon had a cellura-type microstructure, in which fine Nd2d2Fe14e14B grains were surrounded by thin Nd-rich phase. In case of a 2.1at% AI-added melt-spun ribbon, the magnetic properties were as follows: iHc, Br, and (BH)max were 15.5KOe, 7.8KG and 8.5MGOe respectively. And resin bonded magnets were fabricated by mixing optimally quenched ribbon fragments with 2.5wt % polyamide resin, compacting and binding at room temperature. The iHc, Br and (BH)max of bonded magnet were lO.2KOe, 4.4KG and 3.3MGOe respectively. And hot-pressed magnets were made by pressing the overquenched ribbons at high temperature. The magnetic properties of hot-pressed magnets were better than those of bonded magnets, and when the holding time was 8 minutes, the iHc, Br, and (BH)max of the hot-pressed magnet were 1O.8KOe, 7.3KG and 8.0MGOe respectively. Domain structure was mainly maze pattern, which means that the easy magnetization axis could be aligned, and the domain width of the hot-pressed magnets was smaller than that of bonded magnets.

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Mechanism of Crack Formation in Pulse Nd YAG Laser Spot Welding of Al Alloys (Al합금 펄스 Nd:YAG 레이저 점 용접부의 균열 발생기구)

  • Ha, Yong Su;Jo, Chang Hyeon;Gang, Jeong Yun;Kim, Jong Do;Park, Hwa Sun
    • Journal of Welding and Joining
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    • v.18 no.2
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    • pp.213-213
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    • 2000
  • This study was performed to investigate types and formation mechanism of cracks in two Al alloy welds, A5083 and A7NO1 spot-welded by pulse Nd: YAG laser, using SEM, EPMA and Micro-XRD. In the weld zone, three types of crack were observed: center line crack(CCCC), diagonal crack(CDCD), and U shape crack(CUCU). Also, HAZ crack(CHCH), was observed in the HAZ region, furthermore, mixing crack(CMCM), consisting of diagonal crack and HAZ crack was observed.White film was formed at the hot crack region in the fractured surface after it was immersed to 10%NaOH water. In the case of A5083 alloy, white films in C crack and $C_D crack region were composed of low melting phases, Fe₂SiAl8Al8 and eutectic phases, Mg₂Al₃ and Mg₂Si. Such films observed near HAZ crack were also consist of eutectic Mg₂Al₃. In the case of A7N01 alloy, eutectic phases of CuAl₂, Mg32Mg32 (Al,Zn) ₃, MgZn₂, Al₂CuMg and Mg₂Si were observed in the whitely etched films near CCCC crack and CDCD crack regions. The formation of liquid films was due to the segregation of Mg, Si, Fe in the case of A5083 alloy and Zn, Mg, Cu, Si in the case of A7N01 aooly, respectively.The CDCD and CCCC cracks were regarded as a result of the occurrence of tensile strain during the welding process. The formation of CMCM crack is likely to be due to the presence of liquid film at the grain boundary near the fusion line in the base metal as well as in the weld fusion zone during solidification. The CUCU crack is considered a result of the collapsed keyhole through incomplete closure during rapid solidification. (Received October 7, 1999)

Studies on the Interfacial Reaction between electroplated Eutectic Pb/Sn Flip-Chip Solder Bump and UBM(Under Bump Metallurgy) (전해 도금법을 이용한 공정 납-주석 플립 칩 솔더 범프와 UBM(Under Bump Metallurgy) 계면반응에 관한 연구)

  • Jang, Se-Yeong;Baek, Gyeong-Ok
    • Korean Journal of Materials Research
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    • v.9 no.3
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    • pp.288-294
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    • 1999
  • In the flip chip interconnection using solder bump, the Under Bump Metallurgy (UBM) is required to perform multiple functions in its conversion of an aluminum bond pad to a solderable surface. In this study, various UBM systems such as Al1μm/Ti0.2μm/Cu5μm,Al1μm/Ti0.2μm/Cu1μm,al1μm/Ni0.2μm/Cu1μmandAl1μm/Pd0.2μm/Cu1μmAl1μm/Ti0.2μm/Cu5μm,Al1μm/Ti0.2μm/Cu1μm,al1μm/Ni0.2μm/Cu1μmandAl1μm/Pd0.2μm/Cu1μm for flip chip interconnection using the low melting point eutectic 63Sn-37Pb solder were investigated and compared to their metallurgical properties. 100μm100μm size bumps were prepared for using an electroplating process. The effects of the number of reflows and aging time on the growth of intermetallic compounds(IMC) were investigated. Cu6Sn5Cu6Sn5 and Cu3SnCu3Sn IMC were abserved after aging treatment in the UBM system with thick coper (Al1μm/Ti0.2μm/Cu5μm)(Al1μm/Ti0.2μm/Cu5μm). However only the Cu6Sn5Cu6Sn5 was detected in the UBM system with 1μm1μm thick copper even after 2 reflow and 7 day aging at 150C150C. Complete Cu consumption by Cu-Sn IMC growth gives rise to a direct contact between solder inner layer such as Ti, Ni and Pd, and hence to possibly cause reactions between two of them. In this study, however, only for the Pd case, IMC of PdSn. was observed by Cu consumption. UBM interfacial reactions with s이der affected the adhesion strength ot s이der balls after s이der reflow and annealing treatment.

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Thermoelectric Properties of Sb Deficiency N-Type Skutterudite Co4Sb12 (Sb가 결핍된 N형 Skutterudite Co4Sb12의 열전 특성)

  • Tak, Jang-Yeul;Van Du, Nguyen;Jeong, Min Seok;Lee, NaYoung;Nam, Woo Hyun;Seo, Won-Seon;Cho, Jung Young
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.32 no.6
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    • pp.496-500
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    • 2019
  • In this study, we investigate the effect of an Sb-deficiency on the thermoelectric properties of double-filled n-type skutterudite (In0.05Yb0.15Co4Sb12xIn0.05Yb0.15Co4Sb12x). Samples were prepared by encapsulated induction melting, consecutive long-time annealing, and finally spark plasma sintering processes. The Sb-deficient sample contained a CoSb2CoSb2 secondary phase. Both the double-filled n-type skutterudite pristine and Sb-deficient samples showed metallic behavior in electrical conductivity with increasing temperature. The carrier concentration of the Sb-deficient sample decreased compared with that of the pristine sample. Due to a decrease in carrier concentration, the Sb deficient sample showed decreased electrical conductivity and an increased Seebeck coefficient compared with the conductivity and coefficient of the pristine sample. Furthermore, the Sb deficient sample showed an increase in the power factor (σS2σS2); the power factor maximum shifted to athe lower temperature side than ones of the pristine sample. As a result, the Sb-deficient sample represents an improved average figure of merit (ZT) and a ZTmaxZTmax temperature lower than that of the pristine sample. Therefore, we propose that Sb-deficient double-filled n-type skutterudite thermoelectric material (In0.05Yb0.15Co4Sb12xIn0.05Yb0.15Co4Sb12x) be used in the 573~673 K temperature range.